Pakistan let Chinese military engineers photograph and take samples from the US helicopter that was left behind when American special forces killed Osama bin Laden, it has been reported.

If true, the claim would underline the deterioration in US-Pakistani relations since the raid in May in Abbottabad, outside Islamabad in which the al-Qaida leader died.

Members of the Chinese military were allowed to survey the wreckage of the hi-tech helicopter and take samples of its "stealth" skin, which allowed it to enter Pakistan undetected by radar, the Financial Times reported, quoting US sources.

"The US now has information that Pakistan, particularly the ISI [Pakistan's intelligence agency], gave access to the Chinese military to the downed helicopter in Abbottabad," an intelligence figure was quoted as saying.

The FT said it had been told by figures close to the White House and the CIA that Pakistan had given the Chinese access to the helicopter.

It quoted a figure close to the CIA as saying: "We had explicitly asked the Pakistanis in the immediate aftermath of the raid not to let anyone have access to the damaged remains of the helicopter."

There was no immediate comment from the White House. A spokesperson for the US state department said that it was aware of the report.

Amid a worsening relationship between the two countries since the unilateral US raid to kill Bin Laden, the Pakistani military declared last month that it did not need US military aid after the White House confirmed that it would withhold some $800m (£492m) in assistance to the country's armed forces.

Pakistan in turn has expelled US military trainers, limited the ability of US diplomats and other officials to get visas, and restricted CIA operations on its territory.

John Kerry, chairman of the Senate foreign relations committee, went to Pakistan weeks after the raid in a bid to secure the return of the wreckage.

The US fears that cutting-edge military technology in the tail of the helicopter, abandoned after US forces blew up the rest of the craft, could be reverse-engineered in China.

Pakistan said it would return the wreckage as a tentative first step towards hitting the reset button in the two countries' badly damaged relations.